[PATCH][RFC] arm: Add basic support for VIA/WonderMedia SoC's

[arnd@arndb.de (Arnd Bergmann)]

On Monday 12 July 2010 18:50:25 Alexey Charkov wrote:
> 
> This adds basic support for machine initialization, interrupts, timers and
> serial console on VIA/WonderMedia VT8500 and WM8505 Systems-on-Chip.
> 
> Signed-off-by: Alexey Charkov <alchark@gmail.com>
> ---
> 
> These SoC's are used in quite many netbooks and tablets produced in China
> and sold online at relatively low prices (typically below 100 USD).
> 
> Support for WM8505 is known incomplete, while VT8500 is tested by me on the
> hardware and at least prints kernel messages to the serial console with timing
> information.

That was quick. Marek already said most of what I had to say about the
patch, and more. Here are some other minor comments. First of all, I'd
suggest moving all of the descriptory text above into the changelog
(above ---), since that looks like useful information to people that might
want to try out the code.

> +		.section        ".start", "ax"
> +
> +__VT8500_start:
> +		/* Override the obscure machine id from bootloader */
> +#ifdef CONFIG_MACH_BV07
> +		mov	r7, #(MACH_TYPE_BV07 & ~0xf)
> +		orr	r7, r7, #(MACH_TYPE_BV07 & 0xf)
> +#elif defined CONFIG_MACH_WM8505_7IN_NETBOOK
> +		mov	r7, #(MACH_TYPE_WM8505_7IN_NETBOOK & ~0xf)
> +		orr	r7, r7, #(MACH_TYPE_WM8505_7IN_NETBOOK & 0xf)
> +#endif

Do you have any way to detect the actual machines from the existing
boot loader? The way you do it here, the kernel ends up being usable
on only one of the machines at a time.

> +#ifdef CONFIG_MMU
> +/* macro to get at IO space when running virtually */
> +#define IO_ADDRESS(x) ((x) | 0xf0000000)
> +#else
> +#define IO_ADDRESS(x) (x)
> +#endif

I don't know yet what the general consensus in the arm world is about this,
but this looks hacky to me. I'd recommend killing off the IO_ADDRESS macro
and replacing it with proper calls to ioremap.


> diff --git a/arch/arm/tools/mach-types b/arch/arm/tools/mach-types
> index 8f10d24..f5745d1 100644
> --- a/arch/arm/tools/mach-types
> +++ b/arch/arm/tools/mach-types
> @@ -12,7 +12,7 @@
>  #
>  #   http://www.arm.linux.org.uk/developer/machines/?action=new
>  #
> -# Last update: Sat May 1 10:36:42 2010
> +# Last update: Sat Jun 19 13:07:40 2010
>  #
>  # machine_is_xxx	CONFIG_xxxx		MACH_TYPE_xxx		number
>  #

If you need the updated version of this file, it would probably make
sense to build the patch instead a kernel tree that already contains
the latest version, rather than Linus' tree.

> diff --git a/drivers/serial/vt8500_serial.c b/drivers/serial/vt8500_serial.c
> new file mode 100644
> index 0000000..21e0462
> --- /dev/null
> +++ b/drivers/serial/vt8500_serial.c
> @@ -0,0 +1,612 @@
> +/*
> + * drivers/serial/vt8500_serial.c
> + *
> + * Copyright (C) 2010 Alexey Charkov <alchark@gmail.com>
> + *
> + * Based on msm_serial.c, which is:
> + * Copyright (C) 2007 Google, Inc.
> + * Author: Robert Love <rlove@google.com>

This device driver should probably go to the tty maintainer,
Greg Kroah-Hartman <gregkh@suse.de>, with the linux-arm-kernel and
linux-serial at vger.kernel.org mailing lists on Cc.

> +struct vt8500_port {
> +	struct uart_port	uart;
> +	char			name[16];
> +	struct clk		*clk;
> +	unsigned int		ier;
> +};
> +
> +#define UART_TO_VT8500(uart_port)	((struct vt8500_port *) uart_port)

Instead of the direct cast from one type to another, please use
container_of(), which is more type safe.

> diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
> index f10db6e..20ba8c3 100644
> --- a/include/linux/serial_core.h
> +++ b/include/linux/serial_core.h
> @@ -186,6 +186,9 @@
>  #define PORT_ALTERA_JTAGUART	91
>  #define PORT_ALTERA_UART	92
>  
> +/* VIA VT8500 SoC */
> +#define PORT_VT8500    93
> +
>  #ifdef __KERNEL__
>  

In the linux-next tree, number 94 is already being used, so you should
probably use 95 as the next free number when sending the driver to the
serial list.

Otherwise, as I mentioned before, nice work!

	Arnd